This invention relates to foam blowing agent blends of (a) chlorodifluoromethane ("HCFC-22" or "22") with (b) n-pentane (n-C5), i-pentane (i-C5) and/or cyclopentane (c-C5) and to polyol premixes and polyurethane foam compositions containing such blends.
Until now, the leading polyurethane foam blowing agent has been 1,1-dichloro-1-fluoroethane ("141b"), in order to meet the market place requirements for energy, fire performance and cost. At the same time, however, 141b has a high ozone depletion potential ("ODP") of about 0.1. Thus, many foam manufacturers are now investigating the lower ODP pentanes as candidates to replace 141b, as noted for example in an article on "Hydrocarbon Blown Rigid Polyurethane Foam for the Boardstock Industry--A novel Approach" by R. E. Berrier et al which appeared in Polyurethanes Expo '98, Sep. 17-20, 1998. They too, however, have property shortcomings for use in foam, such as high cost and high k-factor performance in foam (thus giving foams with poor thermal insulating properties).
HCFC-22 has also been disclosed, as in U.S. Pat. No. 4,636,529) for use as a foam blowing agent agent. When used alone, it has certain disadvantages such as a high global warming potential ("GWP") of about 1700 and an ODP of about 0.055.
It would therefore be useful to provide the industry with an alternative foam blowing agent which overcomes the deficiencies of 22 or the pentanes alone in terms of properties such as ODP, GWP, cost, and k-factor performance.